Land surface phenometrics and their responses to climatic variables in the semi-arid rangelands of the central Zagros mountains

As climate change accelerates, phenological shifts in vulnerable semi-arid ecosystems remain poorly understood yet are of increasingly critical. Identifying the phenological stages of rangeland ecosystems, and quantifying how climate change affects each stage over time, is essential for effective rangeland management. This study aimed to investigate the long-term trends in land surface phenology (LSP) and the impact of climate variations on LSP in the semi-arid rangelands of Chaharmahal-Va-Bakhtiari (CVB) Province, Iran, from 2000 to 2023. Utilizing satellite data from MODIS NDVI, key LSP metrics were analyzed, including the start of the growing season (SOS), peak of the growing season (POS), end of the growing season (EOS), length of the growing season (LOS), and maximum vegetation greenness (maxNDVI). The findings indicate significant shifts: SOS, POS and EOS are occurring earlier, resulting in shorter growing season in many regions. These changes show strong correlations with climatic variables such as precipitation, temperature, and potential evapotranspiration, with temperature exhibiting the most significant relationship to changes in SOS. The Sen’s slope trend analysis showed that 25.74% of the study area experienced advancements in SOS, 23.2% % in POS, and 32.3% in EOS. Additionally, LOS has decreased in 70% of pixels with significant change. This study demonstrates that phenological patterns in the semi-arid rangelands of CVB are shifting in response to climate change. These findings highlight the need to implement adaptive management strategies to maintain the sustainability of these fragile ecosystems.